This application claims the benefit of Japanese Application 2001-131225, filed Apr. 27, 2001, the entirety of which is incorporated herein by reference.
The present invention relates to a method for removing punched fragments, and a method for producing an article by punching including the method for removing punched fragments. More particularly, the present invention relates to a method for removing punched fragments which can be easily performed on the upper side of a die and is suitable for use in punch work with an extra-fine punch or punch work performed with small punching pitch, and a method for producing an article by punching including the method for removing punched fragments.
In recent years, in the application of punch work using a punch and a die, there has been an increasing demand for forming perforations with smaller diameters and in higher density.
For example, in the case of a circuit board on which electronic components are mounted, it is required to provide numerous small perforations with high precision so that a circuit can be formed with higher density while maintaining high reliability, taking into consideration the cooling effect.
When providing a large number of small perforations on a workpiece for punching, it is essential that the punching operation be performed in such a way that high precision perforations are arranged with uniform spacing, but at the same time it is also important to thoroughly remove punched fragments, which are generated while forming perforations on the workpiece, from the punching machine using a punch and a die, in particular, from the surrounding area of the workpiece to prevent the punched fragments from plugging the product. If the punched fragments are not thoroughly removed and, for example, have entered the perforations of a workpiece for punching, it they will render the product defective, resulting in a reduced product yield. Frequent recurrence of such defects will cause an increase in manufacturing cost, eventually leading to a loss of competitiveness.
FIG. 2(a) and FIG. 2(b) illustrate an example of a conventional process of punch work using a punch and a die.
As shown in FIG. 2(a), a thin workpiece 3 for punching is first mounted on a die 12 as a preparatory step, and the workpiece 3 is perforated with a punch 10 as shown in FIG. 2(b). The punched fragments are removed in the next step, conventionally maintaining the condition as shown in FIG. 2(b), namely, in a condition whereby the punch 10 is protruding into a counterbore 21 of a die 12 after performing punching on the workpiece 3 on the die 12.
Since most of the punched fragments fall into the counterbore 21 side of the die when perforations are formed by the punch 10, the punched fragments have been removed from the counterbore 21 side of the die by means of vacuum suction, or conversely by blowing with compressed air, or alternatively by having the punched fragments adhere to an adhesive medium, so that punched fragments will not remain in the perforations on the workpiece 3. However, it has been observed that a part of the punched fragments sometimes remains attached to the punch 10, causing a plugging by punched fragments that enters the perforation when the punch 10 is pulled up.
Further, the method for removing punched fragments as described above is applicable for a punching machine such as the one illustrated in FIG. 2(a) and FIG. 2(b), which employs a larger diameter for the punch 10 and a greater punching pitch that can allow a wide distance between juxtaposing punches and therefore has ample space in the counterbore 21 of the die. However, when forming perforations on the workpiece 3 with a smaller diameter and in higher density as in the requirement in recent years, it becomes unavoidable to use an extra-fine punch and a narrower punching pitch. For such a punching machine, which employs a smaller diameter for the punch 10 and a narrow punching pitch allowing only a shorter distance between juxtaposing punches, the removal of the punched fragments as described above has been difficult to apply.
For example, along with the trend toward making perforations with an increasing degree of miniaturization and in higher density, it is becoming popular to use punching machines employing an extra-fine punch tip and a minuscule punching pitch, such as the one for which the punching process is as shown in FIG. 3(a) and FIG. 3(b). The difference in structure between this punching machine and a punching machine, for which the punching process is as illustrated in FIG. 2(a) and FIG. 2(b), exists in the counterbore 21 of the die. In the configuration as illustrated in FIG. 2(a) and FIG. 2(b), ample cubic size is secured at the counterbore 21 of the die to permit smooth removal of punched fragments, whereas in the configuration as illustrated in FIG. 3(a) and FIG. 3(b), the counterbore 21 is made much smaller as a means of preventing the die 12 from losing rigidity. As a result, it does not provide sufficient cubic size for a smooth removal operation of punched fragments.
For a punching machine such as described above, in particular, the frontal portion X of the punch 10 with a reduced diameter cannot be made too long from a durability standpoint. At the same time, since it is desirable to have the punching tip protrude into the counterbore 21 of the die for easy removal of punched fragments, the corresponding distance Y of the opening at the die 12 also cannot be made long. This decreases the thickness of the upper side of the counterbore 21 of the die, thereby reducing rigidity of the die 12.
Therefore, it is necessary to make the size of the counterbore 21 of the die smaller to increase rigidity of the die 12. However, since such a design has made it difficult to secure the cubic size required for a removal operation of punched fragments, the removal of punched fragments could not be performed adequately.
When a narrower punching pitch is employed, greater shearing force from the punch 10 works against the workpiece 3, thereby increasing the load on the die 12. Because of this, for the purpose of increasing the strength of the die 12, reinforcement such as a rib member at the counterbore 21 of the die has often been provided. However, such reinforcement has made the configuration of the die 12 more complex, further reducing the space available at the counterbore 21 of the die and thereby making it very difficult to remove the punched fragments according to the above method. This results in insufficient removal of punched fragments, causing punched fragments to remain inside the perforations of the workpiece 3 and eventually leading to a reduced product yield, for example.
As described above, the removal of punched fragments is an important step that has substantial impact on the product yield in punch work, whereas, in particular, for the type of punch work that is required to form perforations with an increasing degree of microminiaturization and in higher density, it is becoming more and more difficult to apply a means for removing punched fragments from the counterbore part underneath a die. While the above suggests that there is a need for any alternative means of completely removing punched fragments from a punching machine so that no punched fragment remains inside the perforations made on a workpiece for punching, a suitable method has not been proposed so far.
The present invention has been made in the light of the above-described problems, and an object thereof is to solve the problems associated with the prior art. More specifically, an object of the present invention is to provide a method for removing punched fragments usable for punch work, which can be easily performed even under the condition where a die is reinforced to allow very narrow space for a counterbore of a die, and, in particular, which can ensure that no punched fragment remains inside the perforations being formed by the punch work and thus can improve the yield of a product being fabricated with the punch work, as well as a method of manufacturing punched products comprising the method for removing punched fragments. An additional object of the present invention is, through its effect, to contribute to improving the mounting technology for installing industrial components consisting mainly of electronic devices, for example by making available products such as a circuit board and the like having numerous small-sized perforations in them.
The present inventors, after extensive study and examination of methods for removing punched fragments which is usable for punch work, have found the following: in the application of a die-punching method to form perforations in a workpiece for punching using a punch and a die, the above objective can be achieved by lifting the workpiece, tightly attached to a stripper, without extracting the punch from a perforation after the perforation is formed in the workpiece, then pushing back the punch in such a way that it protrudes slightly from the bottommost end of the perforation, and providing a removal operation of punched fragments in that condition.
Specifically, the present invention provides a method for removing punched fragments which is usable for punch work using a punch and a die, the method being characterized by forming a perforation in a workpiece for punching by punching the workpiece using the punch, lifting the workpiece, tightly attached to a stripper, from the die without extracting the punch from the perforation, and removing punched fragments in a condition where the punch is pulled up so that the tip portion of the punch protrudes slightly from the bottommost end of the perforation.
In the method for removing punched fragments according to the present invention, it is preferred that the punched fragments should be removed on the die either with an air-blow technique which removes the punched fragments using a flow of compressed air, or with an adhesion technique which removes the punched fragments by having the punched fragments adhere to an adhesive medium.
The method for removing punched fragments according to the present invention can be suitably applied in punch work to form minuscule perforations where an aperture diameter of a perforation or the shortest distance from one edge to an opposing edge of a perforation is 100 xcexcm or less. It is also suitable for use in punch work to form perforations in a workpiece in such high density that the space between the juxtaposing perforations is 100 xcexcm or less.
The present invention provides a method of manufacturing punched products using a punch and a die, which is characterized by comprising:
a step A of piercing a first workpiece for punching by the punch to form a first perforation in the first workpiece,
a step B of lifting the first workpiece, tightly attached to a stripper, from the die without extracting the punch from the first perforation,
a step C of pulling up the punch so that the tip portion of the punch protrudes slightly from the bottommost end of the first perforation,
a step D of removing punched fragments,
a step E of piercing a second workpiece for punching by the punch to form a second perforation in the second workpiece,
a step F of lifting the second workpiece together with the first workpiece without extracting the punch from the second perforation,
a step G of pulling up the punch so that the tip portion of the punch protrudes slightly from the bottommost end of the second perforation, and
a step H of removing punched fragments, and thereafter
laminating a plurality of workpieces to be punched with repetition of the steps E to H.
In the method for producing an article by punching to the present invention, it is preferred to pull up the punch after removing the punched fragments in the step D so that the tip portion of the punch is recessed slightly from the bottommost end of the first perforation, and also to pull up the punch after removing the punched fragments in the step H so that the tip portion of the punch is recessed slightly from the bottommost end of the second perforation. Furthermore, it is preferred to remove the punched fragments on the die by applying either an air-blow technique which removes the punched fragments using a flow of compressed air, or an adhesion technique which removes the punched fragments by having the punched fragments adhere to an adhesive medium.
Moreover, it is preferred to insert a spacer between the die and the stripper when forming perforations using the punch in the steps A and E. Concerning the thickness of such a spacer, it is preferred to make it approximately 5 to 15 xcexcm greater than the total thickness of the workpiece that lies between the die and the stripper, in other words, the sum of the thickness of the workpieces that have already been laminated on the punch and that of the workpiece mounted on the die for forming a new perforation.
The method for manufacturing punched products according to the present invention can be suitably applied in punch work to form minuscule perforations where an aperture diameter of a perforation or the shortest distance from one edge to an opposing edge of a perforation is 100 xcexcm or less. It is also suitable for use in punch work to form perforations in a workpiece in such high density that the space between the juxtaposing perforations is 100 xcexcm or less.